Groundcover Restoration in Forests of the Southeastern United States

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Chapter 3: Tailoring Restoration Strategies to Initial Site Conditionsthe fires tend to be catastrophic or stand-replacing. If lefton the restoration site, this pattern of fire does not promotethe establishment of native flatwoods or sandhill vegetationand can be very difficult to control. Finally, on some sites,the funding necessary to implement restoration activities isgained through the sale of the off-site timber. If clearcuttingis the method chosen to remove off-site pine species in firedependenthabitats, it is necessary that the restorationisttake measures to ensure that fine fuels are present at therestoration site. This is accomplished most often by theintroduction or promotion of native warm-season grassspecies on the restoration site.An advantage of using selective harvest to replace offsitepines with native species is that needle cast from theremaining trees will provide a fuel source for prescribedfire while also maintaining some shade on the site. Thistype of selective logging conversion process is beingtested by the Joseph Jones Ecological Research Center inGeorgia in the restoration of loblolly pine plantations tolongleaf sandhill habitat (Kirkman et al. 2007) and in theApalachicola National Forest in the restoration of slash pineplantations to longleaf flatwoods habitat (C. Hess, USFS,pers. comm.). Kirkman et al. (2007) recommend that avariable canopy retention approach be used as an alternativeto clearcutting because it allows for the maintenance of pinecover necessary for needle cast (aka fine fuel production).Underplanted longleaf pine seedlings will be released instages as the off-site pines are harvested and the restorationwill result in an uneven aged longleaf stand (Kirkman etal. 2007). Harvesting of timber has been implicated inboth soil disturbance and the introduction of non-nativeinvasive species so precautions must be taken to minimizethese potential problems when harvesting at the restorationsite. A review of environmentally sound forest harvestingtechniques is found in Long (2001).EXAMPLE 2. Joseph W. Jones Ecological ResearchCenter restoration of longleaf pine sandhill fromloblolly pine plantations by selective harvest (offsitecanopy species present, groundcover lacking).Goal: Restore longleaf pine sandhill communities ondegraded loblolly pine plantationsFuels Present: YesInvasives Present: NoRestoration Activities:Overstory thinning. Overstory pines were thinnedusing single-tree selection and canopy gaps werecreated ranging in size from 5 - 9m2 per ha. Midstorythinning. Two methods of midstory hardwood controlwere found to be effective, herbicide (Velpar tabletsapplied at 3 kg/ha in May) and prescribed fire alone.Prescribed fire. All sites are burned on a 3-5 yearrotation. Planting. Longleaf pine trees were planted innewly created gaps at variable densities ranging from450 – 1000 trees per ha. Seeding. The site was seededwith wiregrass by hand-dispersal in February with650 g of pure seed per ha.Monitoring: The sites are monitored for speciesrichness, understory hardwood density, andherbaceous ground cover biomass both prior tothe study installation and on 5 year intervals postrestoration.Question 5. How should native groundcover species beintroduced?A major goal of any groundcover restoration project is tomaintain the diversity and cover of native groundcoverspecies at the restoration site. Whether you need to create agroundcover community from scratch or simply augmentkey species to meet restoration goals, many restorationprojects include the planned introduction of nativegroundcover species to the site. This can be a challengingbut rewarding experience for any restorationist. As areminder, prior to the introduction of any native species atthe restoration site, the causes of environmental degradationmust be identified and mediated (soil and hydrologicalalterations, introduction of prescribed fire, removal ofcanopy and midstory biomass) and invasive species shouldbe controlled.There are many considerations to take into account whendetermining which species to introduce and what the bestsource for those species may be, as detailed in Chapter 2 ofthis manual in the section on increasing biodiversity andcoverage of native groundcover species. The practical wayto address these considerations is to start by comparing thecover of the species present at the reference site to thoseat the restoration site. The restorationist needs to identifywhich species have high cover percentages in the referencesite and which species play important ecological roles suchas providing habitat structure, fine fuels for fire, and foodand cover for wildlife. With this list of species in hand,the restorationist needs to determine how these speciesshould be introduced. Depending on the prior historyof human activities at the restoration site (silviculture or| 30 |
Chapter 3: Tailoring Restoration Strategies to Initial Site Conditionsagriculture) and its proximity to natural habitat, there maybe a number of native species present in the seed bank ofthe restoration site. This has been shown for a number offormer pine plantation sites (Hattenbach et al. 1998; Cohenet al. 2004; but see Kirkman et al. 2004; Ruth et al. 2008). Forexample, at The Nature Conservancy’s Apalachicola Bluffsand Ravines Preserve, the soil seed bank of former slashpine plantations provides similar species composition anddiversity as sites that are actively seeded with native seedbulk mixtures (Cox et al. 2004). If time permits, and theproject has a skilled botanist on hand, a soil seed bank studycan be performed at the restoration site to assess the speciescomposition of propagules already present.One keystone species commonly missing from the soilseed bank of degraded Southeastern sites is wiregrass.For many restoration sites, wiregrass is the focal speciesfor groundcover restoration due to the essential role thisspecies plays in carrying fire. If wiregrass is introducedsimultaneously with other native groundcover species,wiregrass survival may be lower than if introduced alone(Aschenbach et al. 2009). For this reason, at sites wherewiregrass establishment is top priority, the use of a two-stepprocess of reestablishing wiregrass first and other nativespecies at a later date may lead to the greatest long-termsuccess.Wiregrass, or any other species identified, can be introducedto the site by either seed or small plants (plugs) dependingon the timeline for restoration, the size of the site, and thebudget for the restoration. Once the list of species needed atthe restoration site is compiled, the next consideration is thesource(s) for those species.The best source for seeds and plants is from a donor siteon or adjacent to the restoration site. If a nearby donor sitecan be found, it is likely to be adapted to the local climateand soil types of the restoration site. As long as the donorsite has large populations (500+) of plants of the speciesfrom which you are planning to harvest seed, the geneticdiversity of the seeds should be sufficient for the futureadaptability of the species at the restoration site. If no donorsites are available and commercial seed/plant sources aresought, it is recommended that seeds of the same ecotypebe used from populations that are both nearby and matchedin hydrological characteristics (e.g., wet vs. dry habitats;Gordon and Rice 1998). The viability of seeds obtained canbe determined by inspecting the seed for mature embryos,testing with tetrazolium blue staining or by a germinationtest (Baskin and Baskin 1998). Finally, these considerationsare not restricted to groundcover species; when plantingtrees or shrubs local adaptation and genetic diversity arealso important. Historically, trees used in plantationswere not genetically diverse and were often not adapted tothe site where they were planted, leading to poor growthperformance and high susceptibility to disease agents(Lambeth and McCullough 1997; McCutchan et al. 1997).Once the seeds are in hand, the restorationist can chose toplant them directly on the site by either broadcast or seeddrill sowing. If seeds were harvested from a donor siteby the collection of bulk silage (using a flail-vac or silagecutter) it has been recommended that seeds are plantedwithin a month after their harvest from the donor site tomaximize germination and prevent spoilage/molding. Ifseeds are collected throughout the year, it is best to storethem in a cool (50-70°F) dry location, in paper or meshbags (not plastic) until sowing in the fall. The seeds ofmany native species have a dormancy mechanism that candelay germination for at least one year. For that reason, ifyou tested the seed viability prior to planting, patience issuggested to allow for seed dormancy.If the restorationist has the resources, native plant seeds canbe propagated in a nursery setting. This method requiresa greater input of resources such as time, water, soil andnursery pots but has a number of benefits:• Quicker establishment• Larger time window for outplanting• Opportunity for community involvementPropagation of wiregrass tubelings at The Nature Conservancy’sApalachicola Bluffs and Ravines Preserve in Bristol, FL. Credits:NWFL TNC.The costs associated with growing wiregrass from seedin a nursery setting should not be underestimated.| 31 |
Page 5: Table of ContentsIntroduction .....
Page 9: Part IDesigning and Executing aGrou
Page 12 and 13: Chapter 1: Planning a Restoration P
Page 15 and 16: Chapter 2Implementing a Restoration
Page 18 and 19: Chapter 2: Implementing a Restorati
Page 27 and 28: Chapter 3Tailoring Restoration Stra
Page 29: Chapter 3: Tailoring Restoration St
Page 33 and 34: Chapter 3: Tailoring Restoration St
Page 35 and 36: Chapter 4Important Considerations f
Page 37 and 38: Chapter 5Costs Associated with Grou
Page 39 and 40: Chapter 5: Costs Associated with Gr
Page 41 and 42: Literature CitedAbrahamson, W. G. a
Page 43 and 44: Literature CitedEgan, D. and E. A.
Page 45 and 46: Literature CitedLeopold, A. 1949. A
Page 48 and 49: Literature CitedTrusty, J. L., and
Page 51 and 52: Chapter 6Location of Groundcover Re
Page 53 and 54: Chapter 6: Location of Groundcover
Page 59: Chapter 6: Location of Groundcover
Page 62 and 63: Chapter 7: Forested Communities of
Page 64 and 65: Chapter 7: Forested Communities of
Page 66 and 67: Chapter 8 : Plant Species of the Fo
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Chapter 8 : Plant Species of the Fo
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Chapter 9Online Resources for Resto
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Chapter 10Comprehensive Bibliograph
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Groundcover Restoration in Forests of the Southeastern United States

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